Electric vehicles powered by trailing cables are used in underground mining operations where internal combustion vehicles are unsafe, and battery powered vehicles are impractical. To avoid dragging the entire cable, a cable reel is typically mounted on the vehicle to pay out and take up cable as the vehicle moves away from and toward the power source to which the cable is connected. Although the mining vehicle is operated to remain facing generally away from the direction of the trailing cable to avoid treading on its own cable, the vehicles must maneuver around corners and over sloped obstacles. Consequently, the trailing cable may extend at an angle substantially offset vertically or horizontally from the rear of the vehicle. This causes the cable to wrap unevenly about the cable reel, risking snags and resulting in a looser, more random wrap of cable about the reel. Because space is at a premium in underground mining vehicles, the larger reel required to accommodate a loosely-wrapped length of cable is disadvantageous.
Various mechanisms have been employed to reciprocate a guide to effect a more uniform wrap of cable or other material on a reel. A conventional ball reverser of the type employed in fishing reels is functionally suitable, but is prohibitively expensive, particularly for such large-scale, heavy duty applications as mining vehicles. In addition, the harsh and abrasive environment in which mining vehicles operate is likely to damage a precisely machined ball reverser.
Although unknown in applications for winding electrical cable in a closely coiled configuration, a conventional reciprocating block such as shown in U.S. Pat. No. 2,650,036 to Berkepeis has been used as a reciprocating thread guide. This apparatus employs a conventional crank and connecting rod assembly for converting rotational motion into reciprocating linear motion of a generally sinusoidal nature. Such a mechanism is unsuitable for a mining vehicle because it is undesirably bulky. The entire mechanism extends well beyond the planar ends of the spool on which the wire is being wound; the crank disk alone must have at least as large a diameter as the desired reciprocating range of the guide.